Serbia has denied it was guilty of genocide during the 1992-1995 war in Bosnia.
The denial came at the International Court of Justice in The Hague, during the opening of its defence against Croatian allegations of ethnic cleansing.
Croatia is seeking reparations from Serbia and Montenegro for the murder and torture of its citizens as well as destruction of property during the war, in which at least 100,000 people were killed.
Serbia's lawyers said the court had no jurisdiction in the case because the country was not a member of the UN at the time the suit was filed and was not subject to the genocide convention.
They also denied that genocide had taken place.
In a court statement Croatian lawyers claimed a Serbian programme of ethnic cleansing yielded 'a form of genocide which resulted in large numbers of Croatian citizens being displaced, killed, tortured, or illegally detained'.
Last year, the tribunal cleared Belgrade of genocide in Bosnia during the break-up of the former Yugoslavia.
It judged the 1995 massacre of thousands of men and boys at Srebrenica in Bosnia to have been an act of genocide, without attributing direct responsibility to Serbia.
Even if the tribunal decides it has jurisdiction, accusations of genocide are extremely difficult to prove as genocidal intent would have to be proven.
The charges against Belgrade would have been strengthened by a judgment against former Serbian President Slobodan Milosevic, but he died in March 2006 shortly before the conclusion of his war crimes trial.
